<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
<!--字面量就是一看就知道是什么数据类型的值-->
  let num=1000
  let str="黑马程序员"
  let arr=[]
  let obj={}
</script>
</body>
</html>